1. Field of the Invention
The present invention relates to an automatic solution mixing apparatus for use with dying, developing, etching solutions and the like.
2. Description of the Prior Art
One of the present inventors has previously proposed an automatic solution mixing apparatus in Japanese Patent Laid Open Application No. 026980/1990. The automatic solution mixing apparatus disclosed in the above-mentioned patent application comprises, as shown in FIG. 1, a plurality of solution distributors 1-1, 1-2, . . . , 1-n (hereinafter represented by the solution distributors 1) which suction and discharge solutions by the reciprocal movement of pistons 1-1b, 1-2b, . . . , 1-nb (hereinafter represented by 1-b) inserted in cylinders 1-1a, 1-2a, . . . , 1-na (hereinafter represented by 1-a). The solution distributors are arranged in a row and are respectively connected to three-way solenoid valves 3-1, 3-2, . . . , 3-n (hereinafter represented by three-way solenoid valves 3) through common ports (COM) thereof. The three-way solenoid valves 3 are connected to solution tanks (not shown) through solution intake pipes 15-1, 15-2, . . . , 15-n, respectively, for receiving solutions from the solution tanks. Also, the three-way solenoid valves 3 are connected to a solution receiver 5 through injection pipes 2-1, 2-2, . . . , 2-n, respectively, for discharging solutions from the solution distributors 1 to the solution receiver 5.
The pistons 1-b of the solution distributors 1 are respectively coupled through couplings 6-1, 6-2, . . . , 6-n to an actuating arm 7 for driving all of the pistons with the same stroke in the same direction. The movement of the arm 7 in the direction as indicated with an arrow A, i.e., back and forth movement, is performed by the normal and reverse rotation of a driving motor 8, and the amount of the back and forth movement is controlled by the number of pulses of the pulse signal fed from a rotary encoder 14 which detects the number of revolutions of the motor 8.
Accordingly, since the back and forth movement of the actuating arm 7 corresponds to that of the pistons 1-b, the amount of movement of the pistons 1-b can be controlled by controlling the amount of the back and forth movement of the arm 7, i.e., the number of pulses fed from the rotary encoder 14. Moreover, since the amount of movement of the pistons 1-b corresponds to the amount of the solution discharged from the distributors 1, by selecting the above-mentioned number of pulses per unit discharge amount in advance, the amount of solution discharged from the cylinders 1-a can be controlled.
The operation of such an automatic solution mixing apparatus will now be hereinafter described. In the first step, with the three-way solenoid valves 3 having their valve passages opened to the solution tanks, the driving motor 8 is so operated as to move the pistons 1-b in a direction of extending the pistons from the cylinders 1-a, i.e., to move the actuating arm 7 backward. Accordingly, the solution is suctioned from the solution tank into each distributor 1 so as to fill the same.
The number of pulses corresponding to the amount of solution to be discharged from each distributor 1 is then set in a control section (not shown), so that the control section will control the operation of the driving motor 8 based upon the number of the above-mentioned set pulses and the number of the pulses supplied from the encoder 14.
Subsequently, the driving motor 8 is rotated to move the actuating arm 7 forward, i.e., to retract the pistons 1-b into the cylinders 1-a to eject air bubbles therefrom, and thereafter perform an operation for mixing a plurality of solutions. In the solution mixing operation, the solutions are discharged in a manner of increasing the amount of solutions discharged from the distributors 1, i.e., increasing the number of the pulses set in the control section, and the control section operates the driving motor 8 to move the actuating arm 7 forward until the discharged amount of the solution reaches specified amount of discharge for each distributor 1 set in the control section. For the distributor 1 in which the discharge of a desired amount of solution has been completed, the three-way solenoid valve 3 located on the discharge side of the cylinder is opened to the solution tank and the solution remaining in the cylinder 1-a (hereinafter called the residual solution) is ejected into the solution tank. This operation is repeated for every solution distributor 1 to mix the solutions.
Although the automatic solution mixing apparatus described above is capable of mixing many kinds of solutions accurately, the solution distributors 1 must be arranged in a row to accommodate a driving gear including the actuating arm 7, driving motor 8 and so on behind the distributors 1, and the number of the solution distributors 1 connected to the driving gear is limited because of the limited length of the actuating arm 7. Therefore, when a large number of solution distributors 1 are required, a plurality of sets of the driving gears and the solution distributors 1 have to be provided, which requires the automatic solution mixing apparatus to be made large.